[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 2/2] libxl: switch NetBSD image file handling to Qemu
On 28/11/12 18:42, Jeff Rizzo wrote: > On 11/28/12 7:48 AM, Roger Pau Monné wrote: >> On 28/11/12 16:29, Thor Lancelot Simon wrote: >> >>> It seems highly unlikely to me that a problem with the loop device driver >>> on Linux is tremendously relevant to NetBSD. >>> >>> But, even if there is some problem with vnd backed by NFS, that hardly >>> seems like it would be a good reason to make a change that reduces I/O >>> throughput for the *non* NFS-backed case by at least 20%. Why would one >>> keep disk images for guests, as a general rule, on NFS, rather than simply >>> doing the NFS mounts on the guests themselves, or using a more sensible >>> protocol like iSCSI? I have to assume most folks using files as disks are >>> storing them on local filesystems on the dom0, and wrecking performance >>> for that case to solve a problem with NFS that may or may not be >>> hypothetical >>> seems like a very, very bad trade-off. >> Quite a lot of people use disk images on NFS, because it's probably the >> easiest shared storage that allows migration of guests. > > I agree that this is a case we should be supporting well. We don't > support migration yet, but I'd like to see this change in the nearish > future. > >> >> Even if disks on NFS was a remote possibility not used by much people I >> don't think it's acceptable to have a Dom0 crash when you try to create >> a guest with a disk on NFS, that is by far much more worse than >> performance degradation in my opinion. > > And, of course, a crash is suboptimal. :) > >> >> If this is not accepted, I will have to detect image format somewhere >> and use qemu when the format is different than raw. > > I would definitely like to see some middle-ground compromise that allows > us to keep decent performance for local files while still allowing them > for NFS. Well, I think the performance is not that bad, given that we are using qemu-traditional and the Dom0 is not MP. We can archive better performance by fixing qemu-upstream to work with NetBSD and of course getting a MP Dom0. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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